V2X Sidelink Channel Design

ABSTRACT

Embodiments are presented herein of apparatuses, systems, and methods for performing vehicle-to-everything sidelink communication. A wireless device may receive vehicle-to-everything resource pool configuration information and sidelink control information. A number of resource elements allocated for a vehicle-to-everything physical sidelink shared channel may be determined based at least in part on the resource pool configuration information and the sidelink control information. A transport block size for the vehicle-to-everything physical sidelink shared channel may be determined based at least in part on the number of resource elements allocated for the vehicle-to-everything physical sidelink shared channel. A low density parity check base graph may be selected for the vehicle-to-everything physical sidelink shared channel based at least in part on the determined transport block size.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.17/059,196, filed Nov. 25, 2020, which is a national phase entry of PCTapplication number PCT/CN2019/121690, entitled “V2X Sidelink ChannelDesign,” filed Nov. 28, 2019, each of which is hereby incorporated byreference in its entirety as though fully and completely set forthherein.

The claims in the instant application are different than those of theparent application and/or other related applications. The Applicanttherefore rescinds any disclaimer of claim scope made in the parentapplication and/or any predecessor application in relation to theinstant application. Any such previous disclaimer and the citedreferences that it was made to avoid, may need to be revisited. Further,any disclaimer made in the instant application should not be read intoor against the parent application and/or other related applications.

FIELD

The present application relates to wireless devices, and moreparticularly to apparatuses, systems, and methods for wireless devicesto perform sidelink communication in vehicle-to-everything (V2X)wireless cellular communications.

DESCRIPTION OF THE RELATED ART

Wireless communication systems are rapidly growing in usage. Oneproposed use of wireless communications is in vehicular applications,particularly in V2X (vehicle-to-everything) systems. V2X systems allowfor communication between vehicles (e.g., via communications deviceshoused in or otherwise carried by vehicles), pedestrian UEs (includingUEs carried by other persons such as cyclists, etc.), and other wirelesscommunications devices for various purposes, such as to coordinatetraffic activity, facilitate autonomous driving, and perform collisionavoidance.

V2X communication has potential to be a source of increasing demand andrange of envisioned uses of wireless communication, which may present avariety of design and development challenges. Accordingly, improvementsin the field in support of such development and design are desired.

SUMMARY

Embodiments are presented herein of apparatuses, systems, and methodsfor performing vehicle-to-everything (V2X) sidelink wireless cellularcommunications.

According to the techniques described herein, a wireless device maydetermine a transport block size for a V2X physical sidelink sharedchannel, and may determine a low density parity check base graph for thephysical sidelink shared channel based at least in part on thedetermined transport block size. In some embodiments, the transportblock size and/or the low density parity check base graph selection mayfurther depend on whether the physical sidelink shared channel is beingused for an initial transmission or a retransmission. Use of such anapproach, and/or one or more other techniques described herein, may helpreduce the likelihood, or potentially avoid altogether, the possibilitythat a different base graph is selected for a retransmission of a dataframe than was selected for an initial transmission of the data frame.

Additionally, techniques are described herein for determining andutilizing a channel occupancy ratio on a per-session basis whenperforming V2X sidelink communication, supporting flexible demodulationreference signal configuration when slot aggregation is configured forV2X sidelink communication, performing resource selection for V2Xsidelink communication, associating physical sidelink shared channelresources with physical sidelink feedback channel resources whenperforming V2X sidelink communication, and performing stage two sidelinkcontrol information resource mapping during V2X sidelink communication,among various other techniques. These various techniques may be usedindividually or in combination to support a V2X sidelink communicationframework, at least according to some embodiments.

Note that the techniques described herein may be implemented in and/orused with a number of different types of devices, including but notlimited to, base stations, access points, cellular phones, portablemedia players, tablet computers, wearable devices, and various othercomputing devices.

This Summary is intended to provide a brief overview of some of thesubject matter described in this document. Accordingly, it will beappreciated that the above-described features are merely examples andshould not be construed to narrow the scope or spirit of the subjectmatter described herein in any way. Other features, aspects, andadvantages of the subject matter described herein will become apparentfrom the following Detailed Description, Figures, and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present subject matter can be obtainedwhen the following detailed description of various embodiments isconsidered in conjunction with the following drawings, in which:

FIG. 1 illustrates an example vehicle-to-everything (V2X) communicationsystem, according to some embodiments;

FIG. 2 illustrates a base station in communication with a user equipment(UE) device, according to some embodiments;

FIG. 3 is an example block diagram of a UE, according to someembodiments;

FIG. 4 is an example block diagram of a base station, according to someembodiments;

FIG. 5 is a flowchart diagram illustrating aspects of an exemplarytechnique for performing sidelink V2X transport block size determinationand LDPC base graph selection, according to some embodiments;

FIG. 6 illustrates aspects of various possible PSCCH and PSSCHmultiplexing options, according to some embodiments;

FIG. 7 is a graph illustrating aspects of an exemplary possible LDPCbase graph selection mechanism, according to some embodiments;

FIGS. 8-9 are flowchart diagrams illustrating further details ofexemplary possible techniques for performing LDPC base graph selectionfor PSSCH decoding, according to some embodiments;

FIG. 10 is a flowchart diagram illustrating aspects of an exemplarypossible technique for performing resource selection for PSSCHtransmission, according to some embodiments;

FIG. 11 illustrates exemplary aspects of a possible approach toperforming resource selection for PSSCH transmission in which certainresources are excluded from consideration, according to someembodiments;

FIGS. 12-13 are flowchart diagrams illustrating aspects of furtherexemplary possible techniques for performing resource selection forPSSCH transmission, according to some embodiments; and

FIG. 14 illustrates exemplary aspects of a possible approach toperforming resource mapping for stage 2 sidelink control information inwhich a frequency domain offset from the subchannel boundary isconfigured, according to some embodiments.

While the features described herein may be susceptible to variousmodifications and alternative forms, specific embodiments thereof areshown by way of example in the drawings and are herein described indetail. It should be understood, however, that the drawings and detaileddescription thereto are not intended to be limiting to the particularform disclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the subject matter as defined by the appended claims.

DETAILED DESCRIPTION Terms

The following is a glossary of terms used in this disclosure:

Memory Medium—Any of various types of non-transitory memory devices orstorage devices. The term “memory medium” is intended to include aninstallation medium, e.g., a CD-ROM, floppy disks, or tape device; acomputer system memory or random-access memory such as DRAM, DDR RAM,SRAM, EDO RAM, Rambus RAM, etc.; a non-volatile memory such as a Flash,magnetic media, e.g., a hard drive, or optical storage; registers, orother similar types of memory elements, etc. The memory medium mayinclude other types of non-transitory memory as well or combinationsthereof. In addition, the memory medium may be located in a firstcomputer system in which the programs are executed, or may be located ina second different computer system which connects to the first computersystem over a network, such as the Internet. In the latter instance, thesecond computer system may provide program instructions to the firstcomputer for execution. The term “memory medium” may include two or morememory mediums which may reside in different locations, e.g., indifferent computer systems that are connected over a network. The memorymedium may store program instructions (e.g., embodied as computerprograms) that may be executed by one or more processors.

Programmable Hardware Element—includes various hardware devicescomprising multiple programmable function blocks connected via aprogrammable interconnect. Examples include FPGAs (Field ProgrammableGate Arrays), PLDs (Programmable Logic Devices), FPGAs (FieldProgrammable Object Arrays), and CPLDs (Complex PLDs). The programmablefunction blocks may range from fine grained (combinatorial logic or lookup tables) to coarse grained (arithmetic logic units or processorcores). A programmable hardware element may also be referred to as“reconfigurable logic”.

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), television system, grid computing system, or otherdevice or combinations of devices. In general, the term “computersystem” can be broadly defined to encompass any device (or combinationof devices) having at least one processor that executes instructionsfrom a memory medium.

User Device—as used herein, may refer generally in the context of V2Xsystems to devices that are associated with mobile actors or trafficparticipants in a V2X system, i.e., mobile (able-to-move) communicationdevices such as vehicles and pedestrian user equipment (PUE) devices, asopposed to infrastructure devices, such as base stations, roadside units(RSUs), and servers.

Infrastructure Device—as used herein, may refer generally in the contextof V2X systems to certain devices in a V2X system that are not userdevices, and are not carried by traffic actors (i.e., pedestrians,vehicles, or other mobile users), but rather that facilitate userdevices' participation in the V2X network. Infrastructure devicesinclude base stations and roadside units (RSUs).

User Equipment (UE) (or “UE Device”)—any of various types of computersystems or devices that are mobile or portable and that perform wirelesscommunications. Examples of UE devices include mobile telephones orsmartphones (e.g., iPhone™ Android™-based phones), portable gamingdevices (e.g., Nintendo DS™, PlayStation Portable™, Gameboy Advance™,iPhone™), laptops, wearable devices (e.g. smartwatch, smart glasses),PDAs, portable Internet devices, music players, data storage devices, orother handheld devices, etc. In general, the term “UE” or “UE device”can be broadly defined to encompass any electronic, computing, and/ortelecommunications device (or combination of devices) which is easilytransported by a user and capable of wireless communication.

Pedestrian UE (PUE) Device—a user equipment (UE) device as regarded inthe context of V2X systems that may be worn or carried by variouspersons, including not only pedestrians in the strict sense of personswalking near roads, but also certain other peripheral or minorparticipants, or potential participants, in a traffic environment. Theseinclude stationary persons, persons not on vehicles who may notnecessarily be near traffic or roads, persons jogging, running, skating,and so on, or persons on vehicles that may not substantially bolster theUE's power capabilities, such as bicycles, scooters, or certain motorvehicles.

Base Station—The term “Base Station” has the full breadth of itsordinary meaning, and at least includes a wireless communication stationinstalled at a fixed location and used to communicate as part of awireless telephone system or radio system.

Processing Element (or Processor)—refers to various elements orcombinations of elements that are capable of performing a function in adevice, such as a user equipment or a cellular network device.Processing elements include, for example, processors and associatedmemory, portions or circuits of individual processor cores, entireprocessor cores, individual processors, circuits such as an ASIC(Application Specific Integrated Circuit), programmable hardwareelements such as a field programmable gate array (FPGA), as well as anyof various combinations of the above.

Channel—a medium used to convey information from a sender (transmitter)to a receiver. It should be noted that since characteristics of the term“channel” may differ according to different wireless protocols, the term“channel” as used herein may be considered as being used in a mannerthat is consistent with the standard of the type of device withreference to which the term is used. In some standards, channel widthsmay be variable (e.g., depending on device capability, band conditions,etc.). For example, LTE may support scalable channel bandwidths from 1.4MHz to 20 MHz. In contrast, WLAN channels may be 22 MHz wide whileBluetooth channels may be 1 Mhz wide. Other protocols and standards mayinclude different definitions of channels. Furthermore, some standardsmay define and use multiple types of channels, e.g., different channelsfor uplink or downlink and/or different channels for different uses suchas data, control information, etc.

Configured to—Various components may be described as “configured to”perform a task or tasks. In such contexts, “configured to” is a broadrecitation generally meaning “having structure that” performs the taskor tasks during operation. As such, the component can be configured toperform the task even when the component is not currently performingthat task (e.g., a set of electrical conductors may be configured toelectrically connect a module to another module, even when the twomodules are not connected). In some contexts, “configured to” may be abroad recitation of structure generally meaning “having circuitry that”performs the task or tasks during operation. As such, the component canbe configured to perform the task even when the component is notcurrently on. In general, the circuitry that forms the structurecorresponding to “configured to” may include hardware circuits.

Various components may be described as performing a task or tasks, forconvenience in the description. Such descriptions should be interpretedas including the phrase “configured to.” Reciting a component that isconfigured to perform one or more tasks is expressly intended not toinvoke 35 U.S.C. § 112, paragraph six, interpretation for thatcomponent.

FIG. 1—V2X Communication System

FIG. 1 illustrates an example vehicle-to-everything (V2X) communicationsystem, according to some embodiments. It is noted that the system ofFIG. 1 is merely one example of a possible system, and that features ofthis disclosure may be implemented in any of various systems, asdesired.

Vehicle-to-everything (V2X) communication systems may be characterizedas networks in which vehicles, UEs, and/or other devices and networkentities exchange communications in order to coordinate trafficactivity, among other possible purposes. V2X communications includecommunications conveyed between a vehicle (e.g., a wireless device orcommunication device constituting part of the vehicle, or contained inor otherwise carried along by the vehicle) and various other devices.V2X communications include vehicle-to-pedestrian (V2P),vehicle-to-infrastructure (V2I), vehicle-to-network (V2N), andvehicle-to-vehicle (V2V) communications, as well as communicationsbetween vehicles and other possible network entities or devices. V2Xcommunications may also refer to communications between othernon-vehicle devices participating in a V2X network for the purpose ofsharing V2X-related information.

V2X communications may, for example, adhere to 3GPP Cellular V2X (C-V2X)specifications, or to one or more other or subsequent standards wherebyvehicles and other devices and network entities may communicate. V2Xcommunications may utilize both long-range (e.g., cellular)communications as well as short- to medium-range (e.g., non-cellular)communications. Cellular-capable V2X communications may be calledCellular V2X (C-V2X) communications. C-V2X systems may use variouscellular radio access technologies (RATs), such as 4G LTE or 5G NR RATs.Certain LTE standards usable in V2X systems may be called LTE-Vehicle(LTE-V) standards.

As shown, the example V2X system includes a number of user devices. Asused herein in the context of V2X systems, “user devices” may refergenerally to devices that are associated with mobile actors or trafficparticipants in the V2X system, i.e., mobile (able-to-move)communication devices such as vehicles and pedestrian user equipment(PUE) devices. User devices in the example V2X system include the PUEs104A and 104B and the vehicles 106A and 106B.

The vehicles 106 may constitute various types of vehicles. For example,the vehicle 106A may be a road vehicle or automobile, a mass transitvehicle, or another type of vehicle. The vehicles 106 may conductwireless communications by various means. For example, the vehicle 106Amay include communications equipment as part of the vehicle or housed inthe vehicle, or may communicate through a wireless communications devicecurrently contained within or otherwise carried along by the vehicle,such as a user equipment (UE) device (e.g., a smartphone or similardevice) carried or worn by a driver, passenger, or other person on boardthe vehicle, among other possibilities. For simplicity, the term“vehicle” as used herein may include the wireless communicationsequipment which represents the vehicle and conducts its communications.Thus, for example, when the vehicle 106A is said to conduct wirelesscommunications, it is understood that, more specifically, certainwireless communications equipment associated with and carried along bythe vehicle 106A is performing said wireless communications.

The pedestrian UEs (PUEs) 104 may constitute various types of userequipment (UE) devices, i.e., portable devices capable of wirelesscommunication, such as smartphones, smartwatches, etc., and may beassociated with various types of users. Thus, the PUEs 104 are UEs, andmay be referred to as UEs or UE devices. Note that although the UEs 104may be referred to as PUEs (pedestrian UEs), they may not necessarily becarried by persons who are actively walking near roads or streets. PUEsmay refer to UEs participating in a V2X system that are carried bystationary persons, by persons walking or running, or by persons onvehicles that may not substantially bolster the devices' powercapabilities, such as bicycles, scooters, or certain motor vehicles.Note also that not all UEs participating in a V2X system are necessarilyPUEs.

The user devices may be capable of communicating using multiple wirelesscommunication standards. For example, the UE 104A may be configured tocommunicate using a wireless networking (e.g., Wi-Fi) and/orpeer-to-peer wireless communication protocol (e.g., Bluetooth, Wi-Fipeer-to-peer, etc.) in addition to at least one cellular communicationprotocol (e.g., GSM, UMTS, LTE, LTE-A, LTE-V, HSPA, 3GPP2 CDMA2000, 5GNR, etc.). The UE 104A may also or alternatively be configured tocommunicate using one or more global navigational satellite systems(GNSS, e.g., GPS or GLONASS), one or more mobile television broadcastingstandards (e.g., ATSC-M/H), and/or any other wireless communicationprotocol, if desired. Other combinations of wireless communicationstandards (including more than two wireless communication standards) arealso possible.

As shown, certain user devices may be able to conduct communicationswith one another directly, i.e., without an intermediary infrastructuredevice such as base station 102A or RSU 110A. As shown, vehicle 106A mayconduct V2X-related communications directly with vehicle 106B.Similarly, the vehicle 106B may conduct V2X-related communicationsdirectly with PUE 104B. Such peer-to-peer communications may utilize a“sidelink” interface such as the PC5 interface in the case of some LTEembodiments. In certain LTE embodiments, the PC5 interface supportsdirect cellular communication between user devices (e.g., betweenvehicles 106), while the Uu interface supports cellular communicationswith infrastructure devices such as base stations. The LTE PC5/Uuinterfaces are used only as an example, and PC5 as used herein mayrepresent various other possible wireless communications technologiesthat allow for direct sidelink communications between user devices,while Uu in turn may represent cellular communications conducted betweenuser devices and infrastructure devices, such as base stations. Forexample, NR V2X sidelink communication techniques can also be used toperform device-to-device communications, at least according to someembodiments. Note also that some user devices in a V2X system (e.g., PUE104A, as one possibility) may be unable to perform sidelinkcommunications, e.g., because they lack certain hardware necessary toperform such communications.

As shown, the example V2X system includes a number of infrastructuredevices in addition to the above-mentioned user devices. As used herein,“infrastructure devices” in the context of V2X systems refers to certaindevices in a V2X system which are not user devices, and are not carriedby traffic actors (i.e., pedestrians, vehicles, or other mobile users),but rather which facilitate user devices' participation in the V2Xnetwork. The infrastructure devices in the example V2X system includebase station 102A and roadside unit (RSU) 110A.

The base station (BS) 102A may be a base transceiver station (BTS) orcell site (a “cellular base station”), and may include hardware thatenables wireless communication with user devices, e.g., with the userdevices 104A and 106A.

The communication area (or coverage area) of the base station may bereferred to as a “cell” or “coverage”. The base station 102A and userdevices such as PUE 104A may be configured to communicate over thetransmission medium using any of various radio access technologies(RATs), also referred to as wireless communication technologies, ortelecommunication standards, such as GSM, UMTS, LTE, LTE-Advanced(LTE-A), LTE-Vehicle (LTE-V), HSPA, 3GPP2 CDMA2000, 5G NR, etc. Notethat if the base station 102A is implemented in the context of LTE, itmay alternately be referred to as an ‘eNodeB’, or eNB. Note that if thebase station 102A is implemented in the context of NR, it mayalternately be referred to as a ‘gNodeB’, or gNB.

As shown, the base station 102A may also be equipped to communicate witha network 100 (e.g., the V2X network, as well as a core network of acellular service provider, a telecommunication network such as a publicswitched telephone network (PSTN), and/or the Internet, among variouspossibilities). Thus, the base station 102A may facilitate communicationbetween user devices and/or between user devices and the network 100.The cellular base station 102A may provide user devices, such as UE104A, with various telecommunication capabilities, such as voice, SMSand/or data services. In particular, the base station 102A may provideconnected user devices, such as UE 104A and vehicle 106A, with access tothe V2X network.

Thus, while the base station 102A may act as a “serving cell” for userdevices 104A and 106A as illustrated in FIG. 1 , the user devices 104Band 106B may be capable of communicating with the base station 102A. Theuser devices shown, i.e., user devices 104A, 104B, 106A, and 106B mayalso be capable of receiving signals from (and possibly withincommunication range of) one or more other cells (which might be providedby base stations 102B-N and/or any other base stations), which may bereferred to as “neighboring cells”. Such cells may also be capable offacilitating communication between user devices and/or between userdevices and the network 100. Such cells may include “macro” cells,“micro” cells, “pico” cells, and/or cells which provide any of variousother granularities of service area size. For example, base stations102A-B illustrated in FIG. 1 might be macro cells, while base station102N might be a micro cell. Other configurations are also possible.

Roadside unit (RSU) 110A constitutes another infrastructure deviceusable for providing certain user devices with access to the V2Xnetwork. RSU 110A may be one of various types of devices, such as a basestation, e.g., a transceiver station (BTS) or cell site (a “cellularbase station”), or another type of device that includes hardware thatenables wireless communication with user devices and facilitates theirparticipation in the V2X network.

RSU 110A may be configured to communicate using one or more wirelessnetworking communication protocols (e.g., Wi-Fi), cellular communicationprotocols (e.g., LTE, LTE-V, etc.), and/or other wireless communicationprotocols. In some embodiments, RSU 110A may be able to communicate withdevices using a “sidelink” technology such as LTE PC5 or NR V2X sidelinkcommunication techniques.

RSU 110A may communicate directly with user devices, such as thevehicles 106A and 106B as shown. RSU 110A may also communicate with thebase station 102A. In some cases, RSU 110A may provide certain userdevices, e.g., vehicle 106B, with access to the base station 102A. WhileRSU 110A is shown communicating with vehicles 106, it may also (orotherwise) be able to communicate with PUEs 104. Similarly, RSU 110A maynot necessarily forward user device communications to the base station102A. In some embodiments, the RSU 110A and may constitute a basestation itself, and/or may forward communications to the server 120.

The server 120 constitutes a network entity of the V2X system, as shown,and may be referred to as a cloud server. Base station 102A and/or RSU110A may relay certain V2X-related communications between the userdevices 104 and 106 and the server 120. The server 120 may be used toprocess certain information collected from multiple user devices, andmay administer V2X communications to the user devices in order tocoordinate traffic activity. In various other embodiments of V2Xsystems, various functions of the cloud server 120 may be performed byan infrastructure device such as the base station 102A or RSU 110A,performed by one or more user devices, and/or not performed at all.

FIG. 2—Communication Between a UE and Base Station

FIG. 2 illustrates a user equipment (UE) device 104 (e.g., one of thePUEs 104A or 104B in FIG. 1 ) in communication with a base station 102(e.g., the base station 102A in FIG. 1 ), according to some embodiments.The UE 104 may be a device with cellular communication capability suchas a mobile phone, a hand-held device, a computer or a tablet, orvirtually any type of portable wireless device.

The UE 104 may include a processor (processing element) that isconfigured to execute program instructions stored in memory. The UE 104may perform any of the method embodiments described herein by executingsuch stored instructions. Alternatively, or in addition, the UE 104 mayinclude a programmable hardware element such as an FPGA(field-programmable gate array), an integrated circuit, and/or any ofvarious other possible hardware components that are configured toperform any of the method embodiments described herein, or any portionof any of the method embodiments described herein.

The UE 104 may include one or more antennas for communicating using oneor more wireless communication protocols or technologies. In someembodiments, the UE 104 may be configured to communicate using, forexample, CDMA2000 (1xRTT/1xEV-DO/HRPD/eHRPD) or LTE using a singleshared radio and/or GSM or LTE using the single shared radio. The sharedradio may couple to a single antenna, or may couple to multiple antennas(e.g., for MIMO) for performing wireless communications. In general, aradio may include any combination of a baseband processor, analog RFsignal processing circuitry (e.g., including filters, mixers,oscillators, amplifiers, etc.), or digital processing circuitry (e.g.,for digital modulation as well as other digital processing). Similarly,the radio may implement one or more receive and transmit chains usingthe aforementioned hardware. For example, the UE 104 may share one ormore parts of a receive and/or transmit chain between multiple wirelesscommunication technologies, such as those discussed above.

In some embodiments, the UE 104 may include separate transmit and/orreceive chains (e.g., including separate antennas and other radiocomponents) for each wireless communication protocol with which it isconfigured to communicate. As a further possibility, the UE 104 mayinclude one or more radios which are shared between multiple wirelesscommunication protocols, and one or more radios which are usedexclusively by a single wireless communication protocol. For example,the UE 104 might include a shared radio for communicating using eitherof LTE or 5G NR (or either of LTE or 1xRTT, or either of LTE or GSM,among various possibilities), and separate radios for communicatingusing each of Wi-Fi and Bluetooth. Other configurations are alsopossible.

FIG. 3—Block Diagram of a UE

FIG. 3 illustrates an example block diagram of a UE 104, according tosome embodiments. As shown, the UE 104 may include a system on chip(SOC) 300, which may include portions for various purposes. For example,as shown, the SOC 300 may include processor(s) 302 which may executeprogram instructions for the UE 104 and display circuitry 304 which mayperform graphics processing and provide display signals to the display360. The processor(s) 302 may also be coupled to memory management unit(MMU) 340, which may be configured to receive addresses from theprocessor(s) 302 and translate those addresses to locations in memory(e.g., memory 306, read only memory (ROM) 350, NAND flash memory 310)and/or to other circuits or devices, such as the display circuitry 304,wireless communication circuitry 330, connector I/F 320, and/or display360. The MMU 340 may be configured to perform memory protection and pagetable translation or set up. In some embodiments, the MMU 340 may beincluded as a portion of the processor(s) 302.

As shown, the SOC 300 may be coupled to various other circuits of the UE104. For example, the UE 104 may include various types of memory (e.g.,including NAND flash memory 310), a connector interface 320 (e.g., forcoupling to a computer system, dock, charging station, etc.), thedisplay 360, and wireless communication circuitry 330 (e.g., for LTE,LTE-A, LTE-V, 5G NR, CDMA2000, Bluetooth, Wi-Fi, GPS, etc.). The UE mayalso include at least one SIM device, and may include two SIM devices,each providing a respective international mobile subscriber identity(IMSI) and associated functionality.

As shown, the UE device 104 may include at least one antenna (andpossibly multiple antennas, e.g., for MIMO and/or for implementingdifferent wireless communication technologies, among variouspossibilities) for performing wireless communication with base stations,access points, and/or other devices. For example, the UE device 104 mayuse antenna 335 to perform the wireless communication.

The UE 104 may also include and/or be configured for use with one ormore user interface elements. The user interface elements may includeany of various elements, such as display 360 (which may be a touchscreendisplay), a keyboard (which may be a discrete keyboard or may beimplemented as part of a touchscreen display), a mouse, a microphoneand/or speakers, one or more cameras, one or more buttons, and/or any ofvarious other elements capable of providing information to a user and/orreceiving or interpreting user input.

As described herein, the UE 104 may include hardware and softwarecomponents for implementing features for performing V2X sidelinkcommunication, such as those described herein. The processor 302 of theUE device 104 may be configured to implement part or all of the methodsdescribed herein, e.g., by executing program instructions stored on amemory medium (e.g., a non-transitory computer-readable memory medium).In other embodiments, processor 302 may be configured as a programmablehardware element, such as an FPGA (Field Programmable Gate Array), or asan ASIC (Application Specific Integrated Circuit). Alternatively (or inaddition) the processor 302 of the UE device 104, in conjunction withone or more of the other components 300, 304, 306, 310, 320, 330, 335,340, 350, 360 may be configured to implement part or all of the featuresdescribed herein, such as the features described herein.

FIG. 4—Block Diagram of a Base Station

FIG. 4 illustrates an example block diagram of a base station 102 (e.g.,base station 102A in FIG. 1 ), according to some embodiments. It isnoted that the base station of FIG. 4 is merely one example of apossible base station. As shown, the base station 102 may includeprocessor(s) 404 which may execute program instructions for the basestation 102. The processor(s) 404 may also be coupled to memorymanagement unit (MMU) 440, which may be configured to receive addressesfrom the processor(s) 404 and translate those addresses to locations inmemory (e.g., memory 460 and read only memory (ROM) 450) or to othercircuits or devices.

The base station 102 may include at least one network port 470. Thenetwork port 470 may be configured to couple to a telephone network andprovide a plurality of devices, such as UE devices 104, access to thetelephone network

The network port 470 (or an additional network port) may also oralternatively be configured to couple to a cellular network, e.g., acore network of a cellular service provider. The core network mayprovide mobility related services and/or other services to a pluralityof devices, such as UE devices 104. In some cases, the network port 470may couple to a telephone network via the core network, and/or the corenetwork may provide a telephone network (e.g., among other UE devicesserviced by the cellular service provider).

The base station 102 may include at least one antenna 434, and possiblymultiple antennas. The at least one antenna 434 may be configured tooperate as a wireless transceiver and may be further configured tocommunicate with UE devices 104 via radio 430. The antenna 434communicates with the radio 430 via communication chain 432.Communication chain 432 may be a receive chain, a transmit chain orboth. The radio 430 may be configured to communicate via variouswireless communication standards, including, but not limited to, LTE,LTE-A, LTE-V, GSM, UMTS, CDMA2000, 5G NR, Wi-Fi, etc.

The base station 102 may be configured to communicate wirelessly usingmultiple wireless communication standards. In some instances, the basestation 102 may include multiple radios, which may enable the basestation 102 to communicate according to multiple wireless communicationtechnologies. For example, as one possibility, the base station 102 mayinclude an LTE radio for performing communication according to LTE aswell as a Wi-Fi radio for performing communication according to Wi-Fi.In such a case, the base station 102 may be capable of operating as bothan LTE base station and a Wi-Fi access point. As another possibility,the base station 102 may include a multi-mode radio which is capable ofperforming communications according to any of multiple wirelesscommunication technologies (e.g., LTE and NR, LTE and Wi-Fi, LTE andUMTS, LTE and CDMA2000, UMTS and GSM, etc.).

As described further subsequently herein, the BS 102 may includehardware and software components for implementing or supportingimplementation of features described herein. The processor 404 of thebase station 102 may be configured to implement or supportimplementation of part or all of the methods described herein, e.g., byexecuting program instructions stored on a memory medium (e.g., anon-transitory computer-readable memory medium). Alternatively, theprocessor 404 may be configured as a programmable hardware element, suchas an FPGA (Field Programmable Gate Array), or as an ASIC (ApplicationSpecific Integrated Circuit), or a combination thereof. Alternatively(or in addition) the processor 404 of the BS 102, in conjunction withone or more of the other components 430, 432, 434, 440, 450, 460, 470may be configured to implement or support implementation of part or allof the features described herein.

FIG. 5—V2X Sidelink Communication

In wireless communications, specifically cellular wirelesscommunications, sidelink communications represent a special kind ofcommunication mechanism between devices that is not carried through abase station, e.g., through eNB/gNB. In other words, the devicescommunicate with each other without that communication going through abase station. In one sense, the devices may be said to be communicatingwith each other directly. Accommodation of such communication, however,requires a new physical layer design.

Many recent studies have identified the need for technical solutions forsidelink design, e.g. a sidelink design in 5G-NR, to meet therequirements of advanced V2X services, including support of sidelinkunicast, sidelink groupcast and sidelink broadcast. A number of specificuse cases have been identified for advanced V2X services, such asvehicle platooning, extended sensors, advanced driving, and remotedriving.

In LTE V2X, broadcast sidelink communications are supported, in whichmaintenance of the sidelink connection is performed using keep-alivemessages communicated between upper layers (e.g., application layers,non-access stratum layers, etc.) of the wireless devices incommunication. NR V2X supports unicast and groupcast sidelinkcommunications, e.g., in addition to broadcast sidelink communications.

In order to support such V2X sidelink communications, a variety ofcommunication channels (e.g., control channels, data channels) may needto be provided. Accordingly, various possible techniques supporting V2Xsidelink communication, including a variety of possible V2X channeldesign features and considerations, are proposed herein. The techniquesmay include for techniques for determining physical sidelink sharedchannel transport block size, techniques for determining a low densityparity code base graph for use in decoding the physical sidelink sharedchannel, and various other techniques.

FIG. 5 is a flowchart diagram illustrating example aspects of suchtechniques, at least according to some embodiments. Aspects of themethod of FIG. 5 may be implemented by a wireless device, such as a PUE104, vehicle 106, any of various other possible wireless devicesillustrated in various of the Figures herein, and/or more generally inconjunction with any of the computer circuitry, systems, devices,elements, or components shown in the above Figures, among others, asdesired. For example, a processor (and/or other hardware) of such adevice may be configured to cause the device to perform any combinationof the illustrated method elements and/or other method elements.

In various embodiments, some of the elements of the methods shown may beperformed concurrently, in a different order than shown, may besubstituted for by other method elements, or may be omitted. Additionalelements may also be performed as desired. As shown, the method of FIG.5 may operate as follows.

In 502, the wireless device may determine a number of resource elementsallocated for a V2X physical sidelink shared channel (PSSCH). The numberof resource elements allocated for the V2X may be determined based atleast in part on V2X resource pool configuration information and/or V2Xsidelink control information that is received by the wireless device.For example, such information may indicate to the wireless device a setof sub-channels that carry the PSSCH, and a number of resource elementsin each such sub-channel, based on which the wireless device may be ableto determine the number of resource elements in the set of sub-channelsthat carry the PSSCH.

At least according to some embodiments, the set of sub-channels thatcarries the PSSCH may also include one or more other physical channelsand/or certain overhead multiplexed with the PSSCH, which may reduce thenumber of resource elements allocated to the PSSCH relative to the totalnumber of resource elements in the set of sub-channels that carry thePSSCH. Accordingly, determination of the number of resource elementsallocated for the V2X PSSCH may further include subtracting the numberof non-PSSCH resource elements in the set of sub-channels that carry thePSSCH from the total number of resource elements in the set ofsub-channels that carry the PSSCH. The result may be determined to bethe number of resource elements allocated for the V2X PSSCH, at least insome instances. It may be the case that the wireless device determineshow many resource elements are allocated to such other physical channelsand/or types of overhead based on the V2X resource pool configurationinformation and/or V2X sidelink control information.

Further, note that, at least according to some embodiments, theallocation of resource elements to the PSSCH and to the various otherchannels and potential overhead may be variable, e.g., from slot toslot, or according to any of various other possible configurations. Forexample, there could be dynamic and/or periodic changes to the number ofresource elements allocated to any or all of first stage sidelinkcontrol information, demodulation reference signals, channel stateinformation reference signals, a physical sidelink feedback channel,phase tracking reference signals (PTRS), AGC, GAP, and/or second stagesidelink control information, among various possibilities. Thus, atleast according to some embodiments, the wireless device may performdetermination of the number of resource elements allocated for the V2XPSSCH on a per-slot basis, and/or otherwise in a dynamic manner based onpotential changes to the number of resource elements allocated for theV2X PSSCH.

In 504, the wireless device may determine a transport block size (TBS)for the V2X PSSCH. The TBS for the V2X PSSCH may be determined based atleast in part on the number of resource elements allocated for the V2XPSSCH. For example, the actual TBS for the V2X PSSCH may be determinedby the wireless device based on the actual number of resource elementsallocated for the V2X PSSCH, the coding rate, the modulation order, andthe number of layers configured for the V2X PSSCH. According to someembodiments, the coding rate, the modulation order, and the number oflayers configured for the V2X PSSCH may be indicated to the wirelessdevice in one or more of the V2X resource pool configuration informationand/or the V2X sidelink control information.

According to some embodiments, in addition to the actual TBS for the V2XPSSCH, the wireless device may determine a model TBS for the V2X PSSCH.The model TBS may be calculated in a manner configured to nullify TBScalculation differences between PSSCH initial transmissions and PSSCHretransmissions. For example, the number of resource elements allocatedto each type of non-PSSCH use of the set of sub-channels that carriesthe PSSCH may be set to a fixed value for the model TBS calculation,such that if the same approach to determining the model TBS is used foreach of a PSSCH initial transmission and the PSSCH retransmission forthe initial transmission, any differences in the number of resourceelements allocated to non-PSSCH uses may be negated, which may result ina consistent model TBS result being obtained for the initialtransmission and the retransmission.

In 506, the wireless device may determine a low density parity check(LDPC) base graph (BG) to use when decoding the PSSCH based at least inpart on the determined TBS. For example, it may be the case that theLDPC BG is selected as either a first LDPC BG or as a second LDPC BG,depending on the determined TBS and the coding rate for the PSSCH.

According to some embodiments, the LDPC BG may be selected based atleast in part on the model TBS (e.g., instead of the actual TBS), if amodel TBS determination such as described above herein is performed bythe wireless device. In such a scenario, it may be the case that LDPC BGselection may be consistent for initial transmissions andretransmissions, e.g., even if the actual TBS would be sufficientlydifferent between an initial transmission and a retransmission to causeLDPC BG selection to differ between the initial transmission and theretransmission if the actual TBS were used to determine the LDPC BG.Note that even if the model TBS is used to determine the LDPC BG, thewireless device may still determine and use the actual TBS whenperforming PSSCH decoding.

As another possibility, the wireless device may consider the actual TBSwhen performing LDPC BG selection, and may also consider whether the V2XPSSCH is being used for an initial transmission or a retransmission(e.g., which the wireless device may determine based at least in part onthe V2X sidelink control information). For example, the wireless devicemay select the LDPC BG for the V2X PSSCH based on the actual TBS and thecoding rate for the V2X PSSCH if the V2X PSSCH is being used for aninitial transmission. Similarly, the wireless device may select the LDPCbase graph for the V2X PSSCH based on the actual TBS and the coding ratefor the V2X PSSCH if the V2X PSSCH is being used for a retransmission,and if the sidelink control information for the initial transmission isunavailable. However, the wireless device may select the same LDPC basegraph for the V2X PSSCH as used in the corresponding initialtransmission if the V2X PSSCH is being used for a retransmission, and ifthe wireless device has the sidelink control information for the initialtransmission.

As a still further possibility, the wireless device may consider themodel TBS when performing LDPC BG selection, and may also considerwhether the V2X PSSCH is being used for an initial transmission or aretransmission. For example, the wireless device may select the LDPC BGfor the V2X PSSCH based on the model TBS and the coding rate for the V2XPSSCH if the V2X PSSCH is being used for an initial transmission.Similarly, the wireless device may select the LDPC base graph for theV2X PSSCH based on the model TBS and the coding rate for the V2X PSSCHif the V2X PSSCH is being used for a retransmission, and if the sidelinkcontrol information for the initial transmission is unavailable.However, the wireless device may select the same LDPC base graph for theV2X PSSCH as used in the corresponding initial transmission if the V2XPSSCH is being used for a retransmission, and if the wireless device hasthe sidelink control information for the initial transmission.

According to some embodiments, the wireless device may also oralternatively determine resource elements allocated to second stagesidelink control information in one or more sub-channels that carry theV2X PSSCH. In such resource element allocation determination, it may bethe case that the resource elements allocated to the second stagesidelink control information are limited from the sub-channel boundaryof the each such sub-channel by a frequency domain offset. This may helpreduce or avoid in-band emission effects on the second stage sidelinkcontrol information, at least according to some embodiments.

According to some embodiments, the wireless device may determine one ormore channel occupancy ratios for its V2X sidelink communication. Forexample, the wireless device may determine its overall or total channeloccupancy ratio, and/or its channel occupancy ratio per priority level(e.g., based on the data priority level of any data communicationsperformed by the wireless device). When determining whether to perform aV2X sidelink transmission, it may be the case that the wireless deviceconsiders whether such a V2X sidelink transmission would cause thewireless device to exceed a channel occupancy ratio limit for thewireless device (e.g., a maximum total channel occupancy ratio, or amaximum channel occupancy ratio for a specific data priority level).

In addition (or as an alternative) to total channel occupancy ratio andper priority level channel occupancy ratios, in some instances, thewireless device may determine one or more session-specific channeloccupancy ratios for its V2X sidelink communication, which may be usedin a similar manner to limit V2X sidelink transmissions by the wirelessdevice to remain within one or more session-specific channel occupancyratios. For example, the wireless device may determine a session-basedchannel occupancy ratio for each unicast or groupcast V2X sidelinkcommunication session of the wireless device, and may determine whetherto perform a V2X sidelink transmission for each such V2X sidelinkcommunication session based at least in part on whether the V2X sidelinktransmission would cause the channel occupancy ratio for that specificV2X sidelink communication session to exceed a channel occupancy ratiolimit for the V2X sidelink communication session. If desired, suchsession based channel occupancy ratio determination and use couldfurther be performed on a per priority level basis.

In some embodiments, it may be the case that slot aggregation could beconfigured for the V2X PSSCH. In such a scenario, it may be useful tosupport the possibility that different DMRS patterns could be used fordifferent types of slots. For example, it could be the case that in sucha scenario the wireless device receives configuration informationindicating a demodulation reference signal (DMRS) configuration for eachof a first slot of the V2X PSSCH, one or more middle slots of the V2XPSSCH, and a last slot of the V2X PSSCH. As another possibility, theDMRS pattern could be configured in terms of the starting DMRS symboland the gap between two DMRS symbols, e.g., to kep similar DMRS densityamong the slots in the slot aggregation. For example, the configurationinformation could indicate a starting DMRS symbol and a gap between DMRSsymbols for the V2X PSSCH.

According to some embodiments, the wireless device may be operating in amanner such that the wireless device performs resource selection for itsV2X sidelink transmissions, which may also be referred to as a “mode 2”wireless device. In such a scenario, it may be beneficial for thewireless device to consider the potential impact on its transmissions ofits own and/or other wireless devices' half-duplex limitations. Forexample, if the wireless device is unable to (or not configured to)transmit and receive simultaneously, scheduling a transmission duringthe same slot that the wireless device is scheduled to receive atransmission by another wireless device may result in the wirelessdevice being unable to receive the transmission. Similarly, if adestination wireless device is unable to (or not configured to) transmitand receive simultaneously, scheduling a transmission to the destinationwireless device during the same slot that the destination wirelessdevice is scheduled to perform a transmission may result in thedestination wireless device being unable to receive the transmission.

Accordingly, at least in some instance, the wireless device may beconfigured to exclude certain resources from selection for sidelinkunicast and/or groupcast transmissions in consideration of suchhalf-duplex issues. For example, as one possible approach to suchresource exclusion, when performing resource selection for a V2Xsidelink transmission from the wireless device, the wireless device maydetermine if one or more resources are reserved for V2X sidelinktransmission by a wireless device that is a destination wireless devicefor the V2X sidelink transmission by the first wireless device, and/ormay determine if one or more resources are reserved for V2X sidelinktransmission to the first wireless device. If one or more resources arereserved for V2X sidelink transmission by a destination wireless device,any resources in the same time slot(s) as the resource(s) reserved forV2X sidelink transmission by the destination wireless device may beexcluded from the resource selection. Similarly, if one or moreresources are reserved for V2X sidelink transmission to the wirelessdevice, any resources in the same time slot(s) as the resource(s)reserved for V2X sidelink transmission to the wireless device may beexcluded from the resource selection.

Alternatively, the wireless device may initially perform resourceselection for a V2X sidelink transmission by the wireless device withoutany half-duplex issue based resource exclusion. In such a scenario, thewireless device may determine if any resources are reserved for V2Xsidelink transmission by a destination wireless device, and/or if anyresources are reserved for V2X sidelink transmission to the wirelessdevice. The wireless device may then remove any resources in the sametime slot as any resources reserved for V2X sidelink transmission by adestination wireless device and/or any resources in the same time slotas any resources reserved for V2X sidelink transmission to the wirelessdevice from the resources selected for the V2X sidelink transmission bythe wireless device.

In a still further possible approach, the wireless device may alsoinitially perform resource selection for a V2X sidelink transmission bythe wireless device without any half-duplex issue based resourceexclusion, and determine if any resources are reserved for V2X sidelinktransmission by a destination wireless device, and/or if any resourcesare reserved for V2X sidelink transmission to the wireless device. Inthis approach, however, the wireless device may drop the V2X sidelinktransmission by the wireless device if any resources selected are in thesame time slot as any resources reserved for V2X sidelink transmissionby a destination wireless device or if any resources selected are in thesame time slot as any resources reserved for V2X sidelink transmissionto the wireless device.

Note that in any of the various approaches to performing resourceselection described herein that include potential resource exclusions inconsideration of the half-duplex issue, the potential resourceexclusions may additionally depend at least in part on the relativepriority levels of the potential transmissions, e.g., if desired. Forexample, the wireless device may determine relative priority levels ofany or all of scheduled V2X sidelink transmission(s) by the destinationwireless device(s), V2X sidelink transmission(s) to the first wirelessdevice, and the V2X sidelink transmission being scheduled the firstwireless device, as applicable. Then, when determining whether toexclude any resources in the same time slot(s) as any resource(s)reserved for V2X sidelink transmission by a destination wireless deviceor any resources in the same time slot as any resource(s) reserved forV2X sidelink transmission to the wireless device from the resourceselection, if the V2X sidelink transmission by the wireless device has ahigher priority than any other scheduled resource usage in a given timeslot, the resources in that time slot may not be excluded from theresource selection process.

According to some embodiments, it may be the case that certainassociations are specified between when data is communicated on a V2XPSSCH and when feedback for that V2X PSSCH communication is scheduled tobe provided on a V2X physical sidelink feedback channel (PSFCH). Forexample, PSFCH resources may be configured with a certain periodicity(e.g., every slot, every 2 slots, every 4 slots, etc.), such that theremay be limitations when PSFCH resources are available on which toprovide feedback. As one possibility, the slot in which feedback for theV2X PSSCH is expected may be specified as the first slot in which a V2Xphysical sidelink feedback channel (PSFCH) is present after a specifiedPSFCH gap. At least in some instances, the value of the PSFCH gap may bedetermined based at least in part on the periodicity of the V2X PSFCH.For example, the PSFCH gap value could be smaller for longer periodicityvalues than for shorter periodicity values. Such an approach may reducethe delay from when data is communicated on a V2X PSSCH and whenfeedback for that V2X PSSCH communication is provided (e.g., for higherPSFCH periodicity values), according to some embodiments.

In some instances, it may also or alternatively be the case that themanner in which the frequency domain resources of the V2X PSFCH that areassociated with a PSSCH transmission is specified. For example, as PSFCHresources may be configured with a certain periodicity, it may be thecase that feedback for multiple PSSCH transmissions is multiplexed onthe PSFCH resources, e.g., in a certain specified manner. Thus, at leastin some instances, the frequency domain resources of the PSFCH that areassociated with a given PSSCH transmission may depend at least in parton the periodicity of the V2X PSFCH.

As a further example, consider a scenario in which a set of V2X PSFCHfrequency resources are used for feedback for a groupcast transmission.For such a scenario, it may be the case that feedback from the multiplerecipients of the groupcast transmission may be multiplexed on the PSFCHresources, e.g., in a certain specified manner. Thus, at least in someinstances, it may be the case that the V2X PSFCH frequency resources onwhich feedback from a given recipient of a V2X PSSCH transmission isexpected are determined based at least in part on a group size of agroupcast group associated with the V2X PSSCH transmission.

FIGS. 6-14 and Additional Information

FIGS. 6-14 illustrate further aspects that might be used in conjunctionwith the method of FIG. 5 if desired. It should be noted, however, thatthe exemplary details illustrated in and described with respect to FIGS.6-14 are not intended to be limiting to the disclosure as a whole:numerous variations and alternatives to the details provided hereinbelow are possible and should be considered within the scope of thedisclosure.

According to some embodiments, it may be the case that NR V2X supportstwo stage SCI. In such a case, information related to channel sensingmay be carried in the first stage of the SCI. The second stage SCI maybe decoded using PSSCH DMRS. Polar coding may be used for the PDCCH andalso applied to second stage SCI. The payload size for the first stageSCI in the case of two stage SCI case may be the same for unicast,groupcast, and broadcast in a resource pool. After decoding the firststage, it may be the case that the receiver does not need to performblind decoding of second stage.

According to some embodiments, it may be the case that, in a resourcepool, within the slots associated with the resource pool, PSFCHresources can be (pre)configured periodically with a period of Nslot(s). N may be configurable, with various values being possible,(e.g., 1 and at least one value that is greater than 1). Theconfiguration may also include the possibility that no resources areprovided for the PSFCH. In this case, HARQ feedback for alltransmissions in the resource pool may be disabled. It may be the casethat HARQ feedback for transmissions in a resource pool can only be senton a PSFCH in the same resource pool. A sequence-based PSFCH format withone symbol (e.g., not including AGC training period) may be supported.This may be applicable for unicast and groupcast including options 1 and2. The sequence of PUCCH format 0, or a sequence derived based at leastin part on that format, may be used. It may be possible that 1 PRB ormultiple PRBs is/are used for this PSFCH format. It may be the case thata X-symbol PSFCH format could be used, with a repetition of theone-symbol PSFCH format (e.g., not including AGC training period), whereX=2 and/or any of various other possible values of X could be supported.It may be the case that a PSFCH format based on PUCCH format 2 could besupported. It may be the case that a PSFCH format spanning all availablesymbols for sidelink in a slot could be supported. It may be the casethat for the periodicity value for how often PSFCH resources areconfigured, (e.g., N slot(s)), N=2 and N=4 are additionally supported.

In NR DL, TBS calculation may be based on coding rate, modulation,number of layers, and the total number of resource elements (REs) forthe PDSCH. The number of REs for the PDSCH is determined by multiplying(number of REs per RB)*(number of RBs).

In NR V2X, several PSSCH and PSCCH multiplexing options may be possible,including ‘option 1A’ 602, ‘option 1B’ 604, ‘option 2’ 606, and ‘option3’ 608, illustrated in FIG. 6 . For example, in the case of ‘option 3’608, the PSCCH and PSSCH resources are combined in a block. It may beuseful for the calculation of the PSSCH resource size to consider thispossible approach to multiplexing the PSSCH and the PSCCH, and it mayaccordingly be useful to provide a new TBS calculation formula thatincludes this consideration. It may further be the case that somesidelink overhead could be carefully excluded from the total channelresources when calculating the PSSCH resource size, at least in someembodiments.

In NR Uu data channel, two LDPC base graphs (BG) may be possible, andmay be designed with different usage conditions. BG selection may dependon code rate and TBS, as shown in FIG. 7 , at least according to someembodiments.

It may be the case that up to 1 blind retransmission is supported in LTEV2X. In NR V2X sidelink, blind retransmission may also be supported. Itmay be the case that a receiving UE obtains just 1 copy of the blindretransmission, e.g., due to half duplex configuration.

In NR V2X sidelink, the PSFCH may occupy the last few symbols in a slot.The PSFCH may be time division multiplexed (TDM) with the PSCCH/PSSCH.As previously noted herein, the PSFCH periodicity may be larger than 1slot, in which case it may be possible that not every slot has PSFCHresources. Furthermore, it may be possible that the PSFCH may not occupyall sub-channels in a slot. For example, the PSFCH may instead onlyoccupy one or several sub-channels in frequency.

Thus, it could occur that the TBS calculation for an initialtransmission may be different from the TBS calculation for a blindretransmission. This TBS mismatch may lead to a mismatch in theselection of the LDPC BG between the initial transmission and theretransmission, which could lead to a decoding error. Accordingly, itmay be useful to implement a TBS calculation approach and/or LDPC BGselection approach that can reduce the likelihood of such a LDPC BGselection mismatch.

As previously noted herein, there may be two LDPC Base Graphs (BG)defined in the NR Uu link. The selection between these two LDPC BGs maydepend on the Transport Block Size (TBS) and nominal Code Rate (CR). Thenominal CR may be the target code rate indicated in the MCS field. TheTBS may be calculated based on the number of resources (i.e., resourceelements or REs) allocated for the PDSCH or PUSCH, the CR, themodulation order, and the number of layers.

In NR V2X sidelink, a similar (or the same) set of two LDPC BGs can beused for the PSSCH. The selection between these two BGs can depend on CRand TBS, e.g., similar to in the NR Uu link. The CR may be indicated inthe MCS field. The calculation of the TBS can be based on a differentprocedure from the NR Uu link, e.g., since the number of REs for thePSSCH may be dynamically changed between slots for any or all of avariety of possible reasons. As one possible reason, the PSSCH DMRS timeand/or frequency density may be dynamically changed, depending on UEspeed(s) and/or other considerations. As another possible reason, it maybe the case that CSI-RS for sidelink unicast may or may not appear ineach PSSCH transmission. As a further possible reason, it may be thecase that the PSFCH occupies some potential PSSCH resources in certainslots and/or in certain sub-channels, and does not occupy thosepotential PSSCH resources in certain other slots and/or sub-channels.Additionally, it may be the case that the second stage SCI could occupysome potential PSSCH resources. As a still further possible reason,possible AGC symbol or GAP symbol RE comb-type multiplexing with thePSSCH could occupy some potential PSSCH resources.

The determination of the TBS may also consider the impact of thepossible use of ‘Option 3’ for PSCCH and PSSCH multiplexing, inparticular including accounting for the REs occupied by the PSCCH. Sincethe PSCCH may appear only in one sub-channel, it may be the case thatthe calculation of PSSCH REs is not directly based on a number of PSSCHREs per PRB or per sub-channel. For example, the calculation of PSSCHREs may be based on the total REs allocated for PSCCH/PSSCH minus thetotal REs allocated for PSCCH.

Thus, the calculation of the TBS may similarly not be based only upon acalculation of PSSCH resources in each RB, e.g., due to itsnon-symmetric distribution. The calculation of TBS may be based on thecalculation of the whole PSCCH/PSSCH resources minus the PSCCH resourcesand other reference signal and/or PSFCH overhead.

According to some embodiments, a receiver UE may determine the actualTBS of PSSCH with the following procedure. The receiver UE may receivethe resource pool configurations, including: PSCCH/PSSCH sub-channelsize N_(RB) ^(SCH), in units of RBs; PSFCH time periodicity, in units ofslots; multiplexing of PSSCH on AGC symbol and/or GAP symbol; PSCCHsymbol duration N_(sym) ^(PSCCH) in units of symbols; and PSCCHfrequency size (if fixed), in units of RBs.

The receiver may decode the SCI, which may include: number ofsub-channels of PSCCH/PSSCH: N_(SCH) ^(PSSCH); DMRS time and/orfrequency domain density; existence and density of CSI-RS; PTRS timeand/or frequency domain density; existence and format of the secondstage of the SCI; and the number of REs of PSCCH: N_(RE) ^(PSCCH).

The receiver may determine the number of REs allocated for PSSCH as:

N _(RE) ^(PSSCH) =N _(SCH) ^(PSSCH) ·N _(RE) ^(SCH) ·N _(slot) ^(PSSCH)−N _(RE) ^(PSCCH) −N _(RE) ^(DMRS) −N _(RE) ^(CSI) ^(RS) −N _(RE)^(PTRS) −N _(RE) ^(PSFCH) −N _(RE) ^(AGC/GAP) −N _(RE) ^(SCI2)   (1),

where:N_(SCH) ^(PSSCH) is the number of sub-channels of this PSCCH/PSSCH. Thisinformation may be obtained from SCI;N_(slot) ^(PSSCH) or is the number of slots of this PSCCH/PSSCH for thecase of slot aggregation. This information may be obtained from SCI;N_(RE) ^(SCH)=N_(RBN) ^(SCH)·N_(RE) ^(RB) is the number of REs of asub-channel, where N_(RE) ^(RB)=12 and N_(RB) ^(SCH) is obtained fromresource pool configuration;N_(RE) ^(PSCCH)=N_(sym) ^(PSCCH)·N_(RE) ^(RB) is the number of REs ofPSCCH, where N_(sym) ^(PSCCH) is the number of symbols of PSCCH, whichmay be (pre)configured by resource pool configuration. N_(RBG) ^(PSCCH)is the number of resource block groups for PSCCH. This number may bepre-defined, preconfigured based on resource pool, or may be obtained byblind decoding of PSCCH. In case of a two stage SCI scheme, N_(RE)^(PSCCH) may be the number of REs of PSCCH for first stage SCI only, ormay be the sum of the number of REs of PSCCH for first stage SCI and thenumber of REs of PSSCH or PSCCH for second stage SCI; N_(RE) ^(DMRS) isthe number of REs of PSSCH DMRS. The time domain density of DMRS may bedynamically changed and may be indicated in SCI. The frequency domaindensity of DMRS may be predefined or may be dynamically changed andindicated in SCI;N_(RE) ^(SCI_RS) is the number of REs of CSI-RS in PSSCH. The existenceof this overhead may be indicated in SCI. The density of CSI-RS in PSSCHmay be predefined, or preconfigured, or indicated in SCI;N_(RE) ^(PTRS) is the number of REs of PSSCH PTRS. The time domaindensity of PTRS may be dynamically changed based on MCS and PSSCHscheduled frequency resources.N_(RE) ^(PSFCH) the number of REs of PSFCH. This field may or may notexist for every slot in a resource pool. If it exists for the slot, thenthe last few symbols spanning over part or all sub-channel may be usedfor PSFCH;N_(RE) ^(AGC/GAP) is the number of REs for AGC and GAP; andN_(RE) ^(SCI2) is the number of REs for SCI part (stage) 2. This fieldmay or may not exist. If it exists, the number of REs may be indicatedin SCI part 1.

N_(info)=N_(RE) ^(PSSCH)·R·Q_(m)·vQ_(m)v The receiver may calculate anintermediate number of information bits

N_(info)=N_(RE) ^(PSSCH)·R·Q_(m)·vQ_(m)v where R is the coding rate, isthe modulation order and is the number of layers.

N_(info)=N_(RE) ^(PSSCH)·R·Q_(m)·vQ_(m)v

The receiver may use either a TBS table or a TBS formula to calculatethe actual TBS using this information.

The number of REs allocated to PSSCH calculated by the receiver may bedifferent between an initial transmission and a retransmission due toone or more of various possible reasons. For example, the PSSCH in theinitial transmission may share the slot with a PSFCH, while the PSSCH inthe retransmission may not share the slot with a PSFCH, or vice versa.As another possibility, the PSSCH in the initial transmission mayinclude CSI-RS or PTRS, while the PSSCH in retransmission may notinclude CSI-RS or PTRS, or vice versa. As a still further possibility,the PSSCH in the initial transmission may have a different DMRS symboldensity from the PSSCH in the retransmission, or vice versa.

Thus, it may be possible for the calculated actual TBS for the initialPSSCH transmission to be different from the calculated actual TBS forthe PSSCH retransmission, e.g., based on the preceding TBS determinationprocedure described herein. Accordingly, if the LDPC BG selection isbased on the calculated actual TBS for each PSSCH transmission, theselected BG may be different for a PSSCH initial transmission and aPSSCH retransmission, which may cause a PSSCH decoding error. There maybe multiple possible techniques for avoiding such a LDPC BG selectiondiscrepancy. For example, one of the following approaches (or acombination of multiple of the following approaches) may be applied,according to some embodiments.

In a first approach, the LDPC BG selection may be based on the codingrate and actual TBS of the initial PSSCH transmission if possible. FIG.8 shows an exemplary such LDPC BG selection procedure at Rx UE side. In802, a receiving UE receives resource pool configurations, includingPSFCH periodicity, PSSCH/PSSCH sub-channel size, PSCCH symbol durations,etc. In 804, the UE may decode the SCI for a certain PSSCH transmission,and may obtain PSCCH resource size, coding rate, modulation order, layernumber, retransmission index. In 806, based on equation (1), the UE maycalculate the number of REs of PSSCH, and may further calculate theactual TBS using this information. In 808, from the SCI parameter“retransmission index”, the UE may be able to determine whether thecurrent PSSCH transmission is an initial transmission or aretransmission. For an initial transmission, in 810, the UE maydetermine the LDPC BG based on the calculated actual TBS and codingrate. For a retransmission, in 812, the UE may check whether it hasdecoded the SCI of the initial PSSCH transmission. If so, in 814, the UEmay use the selected LDPC BG from the initial transmission. Otherwise,in 816, the UE may determine the LDPC BG based on the calculated actualTBS and coding rate. In 818, the UE may decode the PSSCH using theselected LDPC BG and the actual TBS.

In a second possible approach, the LDPC BG selection may be based on thecoding rate and a “model” TBS. The model TBS may be designed such thatthe potentially different overhead between a PSSCH initial transmissionand a PSSCH retransmission is nullified or dismissed. FIG. 9 is aflowchart diagram illustrating aspects of such a possible approach,according to some embodiments.

The model TBS determination procedure may include, in 902, receiving theresource pool configurations, e.g., with the same information previouslydescribed herein for actual TBS determination procedure.

In 904, the receiver may decode the SCI, which may include the numbersub-channels of PSCCH/PSSCH (N_(SCH) ^(PSSCH)), number of REs of PSCCH(N_(RE) ^(PSCCH)) and the number of REs of PSSCH for SCI stage 2 (N_(RE)^(SCI2)).

In 906, the receiver may calculate the model TBS. To do so, the receivermay determine the number of REs allocated for the PSSCH as in equation(1), where the dynamically changed fields are fixed or preconfigured,rather than by indicated in SCI. For example, in equation (1), N_(RE)^(DMRS) may be fixed or preconfigured, no matter what the actual timeand/or frequency domain density of DMRS are. Similarly, N_(RE) ^(CSI_RS)or N_(RE) ^(PTRS) may be fixed or preconfigured, no matter whetherCSI-RS or PTRS is actually transmitted in PSSCH. For example, this fieldmay always be set to 0. N_(RE) ^(PSFCH) may be fixed or preconfigured,no matter whether the actual PSFCH exists or not. For example, thisfield may always be set to 0. For example, this field may always be setto 0 if no PSFCH resources are allocated; this field may always be setto a non-zero value if PSFCH periodicity is 1 slot; and this field maybe configured to 0 or a non-zero value if PSFCH periodicity is 2 or 4slots, as one possibility. N_(RE) ^(AGC/GAP) may be fixed orpreconfigured, no matter whether or not PSSCH is actually multiplexed onAGC symbol or GAP symbol. For example, it may always be assumed that thePSSCH is not multiplexed on AGC symbol or GAP symbol.

The receiver may calculate a model intermediate number of informationbits N_(info)=N_(RE) ^(PSSCH)·R·Q_(m)·v, where R is the coding rate,Q_(m) is the modulation order and v is the number of layers.

The receiver may use either a TBS table or a TBS formula to calculatethe model TBS using this information.

Note that in such an approach, the receiving UE may calculate both modelTBS and actual TBS. For example, as shown, in 908, the UE may calculatethe actual TBS. In 910, the receiving UE may use the model TBS forselecting LDPC BGs, and, in 912, may use the selected LDPC BG and theactual TBS in the PSSCH decoding.

In a third approach, for a PSSCH initial transmission, the LDPC BGselection may be based on the coding rate and model TBS in the initialPSSCH transmission. For a PSSCH retransmission, the LDPC BG selectionmay be based on the previous PSSCH transmission (of the same TB) if thisinformation is available, or the LDPC BG selection may be based on thecoding rate and model TBS of the retransmitted PSSCH if the LDPC BGselection in the PSSCH previous transmission (of the same TB) is notavailable. Then, the PSSCH decoding may be based on the selected LDPC BGand the actual TBS.

In LTE V2X, the metric of channel occupancy ratio (COR) may be evaluatedby each UE. For example, at a subframe n, the total number ofsub-channels used for a UE's transmission in subframes [n−a, n−1] andgranted in subframes [n, n+b] divided by the total number ofsub-channels in the transmission pool over [n−a, n+b] may be specifiedas being equal to the COR of the UE, at least according to someembodiments. In some instances, the COR may further be calculated perpriority level, i.e., COR(p_(i)) for the data priority level p_(i).

The metric of COR may be aimed to limit the maximum channel occupancy ofa single UE. In NR V2X, a UE may have sidelink broadcast, unicast andgroupcast. For sidelink unicast or groupcast, it may be feasible torestrict the maximum channel occupancy of each single session (or link).For sidelink unicast, the session is shared by two UEs; for sidelinkgroupcast, the session is shared by a group of UEs.

A session-based channel occupancy ratio (CR or COR) at slot n may bedefined as the total number of sub-channels used for a session member'stransmission in slots [n−a, n−1] and granted in slots [n, n+b], dividedby the total number of sub-channels in the transmission pool over [n−a,n+b], at least as one possibility.

For example, in sidelink unicast with UE-A and UE-B, UE-A may calculatethe summation of the number of sub-channels used for its transmission toUE-B, and the number of sub-channels used for UE-B's transmission toUE-A. The division of this summation over the total number ofsub-channels in the transmission pool may be specified as thesession-based COR for the sidelink unicast session between UE-A andUS-B.

The session-based COR could also be calculated per priority level, i.e.,COR(p_(i), session) for the data priority level p_(i) for sidelinksession j. The session-based COR could be used for congestion controlpurpose. For example, a per priority level threshold may bepre-configured or may be configured during session setup process, e.g.,COR_(limit)(p_(i), session_(j)). If a mode 2 UE has some datatransmission for sidelink unicast or groupcast, after resourceselection, it may check if the current transmission to the sidelinksession will exceed the limitation configured for this session, i.e.,Σ_(k≥i)COR(p_(k), session_(j))>COR_(limit)(p_(i), session_(j)). If so,then the sidelink unicast/groupcast transmission may be dropped.

In an alternative way, the session-based COR may be used in the resourceselection procedure by a mode 2 UE for its sidelink unicast or groupcasttransmission. For example, the upper bound on session-based COR mayimpact the percentage of the candidate resources to be reported tohigher layer by the UE.

The session-based COR may be used independently, or may be jointly usedwith UE-based COR (e.g., the legacy LTE V2X COR). For example, both acondition on session-based COR, i.e., Σ_(k≥i)COR(p_(k),session_(j))≤COR_(limit)(p_(i), session_(j)) and a condition on UE-basedCOR, i.e., Σ_(k≥i)COR(p_(k))≤COR_(limit)(p_(i)), could be configured andused in parallel, if desired.

Note that for in-device coexistence of LTE and NR sidelinks, it may bethe case that a short time scale TDM approach is feasible when thetraffic load of LTE and NR is at or below an acceptable level. Todetermine whether or when to use such a short time scale TDM approach, ametric of LTE or NR traffic load may be defined. A threshold on thismetric could be configured, e.g., such that if the metric is above thethreshold, the short time scale TDM solution is not used.

One possible metric can be the COR for LTE sidelink, or COR for NRsidelink. Let COR_(LTE) be the COR for LTE sidelink and let COR_(NR) bethe COR for NR sidelink. The COR_(LTE) can be per UE or per UE perpriority level. The COR_(NR) can be per UE, per UE per priority level,or per UE per sidelink session. One or more COR thresholds for LTEsidelink (e.g., COR_(LTE) ^(limit)) and one or more COR thresholds forNR sidelink (e.g., COR_(NR) ^(limit)) can be configured.

As one possibility, the configuration can be per resource pool, e.g.,via common configuration. As another possibility, the configuration canbe UE specific, e.g., via dedicated configuration.

If the measured COR_(LTE) is below the threshold COR_(LTE) ^(limit),and/or the measured COR_(NR) is below the threshold COR_(NR) ^(limit),then the short time scale TDM approach may be used.

In LTE V2X Release 15, the DMRS symbols may have fixed locations in thetime domain. Among 14 symbols in a subframe, the first symbol is AGC andthe last symbol is a GAP symbol. Hence, there are 12 symbols for dataand DMRS. The DMRS symbols are located at the 2, 5, 8, 11 symbols. Thisdesign may ensure that every data symbol is located next to a DMRSsymbol.

In NR V2X, slot aggregation may be used to support large payload sizes.In slot aggregation, the overhead of AGC and GAP may be reduced, sinceamong the consecutive slots for the same data, the GAP and AGC may notbe needed.

For example, in the first slot of slot aggregation, the first symbol maybe for AGC and the last symbol may be for data or DMRS. In the last slotof slot aggregation, the first symbol may be for data or DMRS and thelast symbol may be for GAP. In the middle slots of slot aggregation,both the first symbol and the last symbol may be for data or DMRS.

The DMRS configuration may consider this feature and have different DMRSpattern indices for different types of slots. In one approach, insteadof a single DMRS pattern being indicated (e.g., in SCI), multiple DMRSpatterns may indicated in the case of slot aggregation. For example, onefor the first slot, one for the last slot, and one or more for themiddle slots (e.g., if applicable, such as if more than 2 slots areaggregated).

In an alternative approach, the DMRS pattern indication could be interms of the starting DMRS symbol and the gap between two DMRS symbols.In this way, a similar DMRS density among the slots in the slotaggregation may be specified.

If the data for V2X transmissions are for unicast or groupcast, then inthe resource selection procedure, it may be the case that the targetUE(s) transmissions are considered. This may help reduce the potentialimpact of the half-duplex issue at the target UE(s). For example, ifsome periodic resources are reserved by one or more target UEs, then thetransmitting UE may be able to determine that the unicast or groupcasttransmissions at the corresponding slots may not be received by thetarget UE due to the half duplex issue. Hence, it may be the case thatall of the resources in the slots reserved by target UEs for theirtransmissions are excluded during the resource selection procedure.

In a first approach to implementing such resource selection exclusion,in the resource selection procedure, if the sidelink data is for unicastor groupcast, then the destination (group) ID may be considered.Specifically, if the destination UEs have reserved resources at certainslots, then these slots may be avoided. The principle may be that thesource UE treats the destination UE(s) reserved resources as its ownreserved resources.

In a second approach, if the sidelink data is for unicast or groupcast,the legacy resource selection procedure may be applied. After thecandidate resources are selected, the source UE may remove certaincandidate resources if the corresponding time unit is used by thedestination UE for its transmissions. Then the modified candidateresources may be reported to higher layer for final resourcedetermination.

In a third approach, if the sidelink data is for unicast or groupcast,the legacy resource selection procedure may be applied, and thecandidate resources may be reported to higher layer for final resourcedetermination. In case the final selected resource has the timeconflict, i.e., the destination UE will use this time unit for itstransmissions, then the resource may dropped and it may be the case thatthe source UE does not perform the sidelink transmission. A resourcereselection procedure may be triggered subsequently.

Similarly, in the source UE's resource selection procedure, it may bethe case that the source UE reception in sidelink unicast or groupcastis considered. This may help reduce the potential impact of thehalf-duplex issue at the source UE. For example, if some periodicresources are reserved by another UE to unicast or groupcast to thesource UE, then the source UE may be able to determine that anytransmissions at the corresponding slots may not be available for itssidelink data transmissions due to the half duplex issue. Hence, it maybe the case that all of the resources in the slots which are reserved byanother UE for sidelink unicast/groupcast transmission to the source UEare excluded during the resource selection procedure.

In a first approach to implementing such resource selection exclusion,in the resource selection procedure, the principle may be that thesource UE treats another UE's reserved resources (for the unicast orgroupcast to the source UE) as the source UE's own reserved resources.

Furthermore, the additional resource exclusion may depend on data QoS.For example, if the source UE's data to transmit has a lower prioritythan the source UE's unicast/groupcast data reception, then theadditional resource exclusion may be applied. Otherwise, the additionalresource exclusion may not be applied.

The additional resource exclusion in the resource selection procedurebased on if any resources are reserved for transmission(s) to the sourceUE can be used together with the additional resource exclusion based onif any resources are reserved for transmission(s) by the destinationUE(s).

FIG. 10 shows an exemplary resource selection procedure in considerationof half duplex issue at both source UE and destination UE(s). As shown,in 1002, the source UE may receive higher layer parameters for resourceselection. In 1004, resource selection window parameters may bedetermined, where the set of all resources may be defined as S_(M). In1006, a resource exclusion RSRP threshold “Th” may be determined. In1008, a set of resources S_(A) may be set equal to S_(M). In 1010, allcandidate resources from S_(A) without channel monitoring may beexcluded. In 1012, time units during which the source UE expects toreceive sidelink unicast or groupcast transmissions may be excluded. In1014, time units during which the destination UE is planning to maketransmissions may be excluded. In 1016, any candidate resources fromS_(A) that are reserved by another UE may be excluded. In 1018, it maybe determined if |SA|<B₁|SA|. If yes, “Th” may be increased and theprocedure may return to step 1008. If no, in 1020, the first B₂|SM|resources in S_(A) may be saved, with ranking based on sidelink RSSI.

FIG. 11 shows an example of resource exclusion for sidelink unicast orgroupcast. As shown, the resources reserved by UEs other than unicast orgroupcast destination UEs are excluded. If a unicast or groupcastdestination UE reserves a resource, then the resources in the whole slotare excluded. In other words, this slot may be marked as an unusableslot. Additionally, if a UE has some unicast or groupcast sidelinkreception at a resource, then the resources in the whole slot areexcluded.

FIG. 12 is a flowchart diagram illustrating another possible approach toperforming resource selection with additional candidate resourcesremoval in consideration of the half duplex issue at both source UE anddestination UE(s) for sidelink unicast or groupcast. As shown, in 1202the (e.g., legacy) physical layer resource selection procedure may beapplied. In 1204, after the candidate resources are selected, the sourceUE may remove certain candidate resources if the corresponding timeunit(s) is (are) used by the source UE for its unicast or groupcast datareception. In 1206, it may be determined if the resource selection isfor a broadcast sidelink transmission. If not, in 1206, the source UEmay remove certain candidate resources if the corresponding time unit(s)is (are) used by any destination UEs for their unicast or groupcast datatransmission. In 1208, the (possibly modified) candidate resources maybe reported to higher layer for final resource determination.

FIG. 13 shows a still further exemplary procedure of resource selectionwith final resource dropping in consideration of half duplex at bothsource UE and destination UE(s) for sidelink unicast or groupcast. Asshown, in such an approach, in 1302, the legacy resource selectionprocedure may be applied, and in 1304 the candidate resource(s) may bereported to a higher layer for final resource determination. In 1306, anindication of the final resource(s) selected for the sidelinktransmission may be received from the higher layer. In 1308, it may bedetermined if any of the selected resource(s) have a time domainconflict with the source UE for its unicast or groupcast reception. In1310, in the case that the final selected resource(s) have a timeconflict with the source UE for its unicast or groupcast reception, thenthe resource(s) may be dropped and it may be the case that the source UEdoes not perform the sidelink transmission. In 1312, if there is no timeconflict with the source UE for its unicast or groupcast reception, itmay be determined if the resource(s) is (are) for broadcast sidelinktransmission. If so, in 1314, the final resource(s) may be used for thebroadcast sidelink transmission. If the resource(s) is (are) not forbroadcast sidelink transmission, in 1316, the source UE may furtherdetermine if the selected resource(s) have a time conflict with anydestination UEs for their unicast or groupcast data transmission. Ifnot, the procedure may proceed to step 1314 and the final resource(s)may be used for the transmission. If so, the procedure may proceed tostep 1310, the resource(s) may be dropped and it may be the case thatthe source UE does not perform the sidelink transmission. In case thesource UE does not perform the sidelink transmission, a resourcereselection procedure may be triggered subsequently.

It may be the case that PSFCH resources can have a periodicity of 1, 2or 4 slots. For a PSFCH resource periodicity of more than 1 slot, theadditional resource exclusion, in consideration of source UE sidelinkunicast/groupcast reception, can be extended so as to avoid the casewhere a UE has to transmit data and receive HARQ feedback at the sametime. For example, with the implicit association between PSSCH andPSFCH, the time slot with the PSFCH may be associated with multiple timeslots of PSSCH if the PSFCH resource periodicity is more than 1 slot. Inthe resource selection procedure for sidelink unicast/groupcasttransmission with HARQ feedback enabled, if a source UE has someunicast/groupcast sidelink reception with HARQ feedback enabled at acertain time slot, then not only the resources in that time slot may beexcluded, but also the resources in neighbor time slots which share thesame PSFCH slot with that time slot may be excluded, at least accordingto some embodiments.

For a given resource pool, PSFCH resources could be at the last fewsymbols of a slot, while the PSFCH periodicity, m, could be every singleslot, every 2 slots, or every 4 slots, depending on resource poolconfiguration, at least in some instances. It may be the case that for aPSSCH transmission with its last symbol in slot n, when thecorresponding HARQ feedback is due for transmission, it is expected tobe in slot n+a, where a is the smallest integer larger than or equal toK with the condition that slot n+a contains PSFCH resources.

For different values of PSFCH periodicity m, the maximum number of slotsof PSSCH to PSFCH delay can be different. For example, if m=1, then thePSSCH to PSFCH gap is K slots; if m=2, then the PSSCH to PSFCH gap canbe K or K+1 slots; if m=4, then the PSSCH to PSFCH gap can be K, K+1,K+2, or K+3 slots. Hence, the overall PSFCH latency may depend on PSFCHperiodicity. The PSSCH to PSFCH gap K could depend on PSFCH periodicitym. For example, in general, for larger values of m, K may be smaller.Let K_(m) be the gap corresponding to PSFCH periodicity m, m=1,2,4. Inthis scenario, it may be the case that K₄≤K₂≤K₁. For example, it couldbe the case that K₁=4, K₂=₃ and K₄=₁. In some instances, the possiblevalues K could be configured such that the largest PSSCH to PSFCH gapmay be no larger than a specified number of slots (e.g., 4 slots, in thepreceding example), e.g., no matter the PSFCH periodicity. The selectionof K can also depend on the sub-carrier spacing of the resource pool orsidelink bandwidth part, in some instances. For example, in general, itmay be the case that for larger sub-carrier spacing, the value K mayalso be larger, e.g., to achieve data latency requirements, at leastaccording to some embodiments.

For PSFCH periodicity m, e.g., m=1, 2, 4 slots, m PSFCH corresponding tom PSSCH transmissions may share the whole i-th sub-channel at slotn+k_(m). It may be the case that the m PSFCH equally share the resourceson the same sub-channel in the frequency domain. For example, the j-th,j=1, . . . , m, PSFCH may occupy the j-th

$\left\lfloor \frac{N_{RB}^{subchannel}}{m} \right\rfloor$

RBs of this subchannel, where N_(RB) ^(subchannel) is the configuredsub-channel size of the resource pool. The j-th PSFCH may correspond tothe PSSCH transmission on the i-th sub-channel at slot n−(m−j). Notethat it may be possible that mod(N_(RB) ^(subchannel), m)≠0. One of thefollowing schemes may be used for the additional resources in such ascenario, among various possibilities:

The last mod (N_(RN) ^(subchannel), m) RBs of a sub channel may be leftunused.

The last mod (N_(RB) ^(subchannel), m) RBs of a sub-channel may be usedby the last (i.e., the m-th) PSFCH.

The last mod (N_(RN) ^(subchannel), m) RBs of a sub-channel may be usedby a PSFCH corresponding to sidelink groupcast to support HARQ feedbackfrom multiple receiving UEs. The usage of the last mod(N_(RN)^(subchannel), m) RBs of a sub channel may be reserved for such use inthe SCI of a PSSCH transmission.

Based on such a frequency domain association scheme, the allocated PSFCHfrequency resource for a PSSCH transmission may have

$\left\lfloor \frac{N_{RB}^{subchannel}}{m} \right\rfloor$

RBs. If a PSFCH format such as NR PUCCH format 0 is used, then it may bethe case that it occupies 1 PRB. If

${\left\lfloor \frac{N_{RB}^{subchannel}}{m} \right\rfloor > 1},$

then the allocated PSFCH resource may be more than the required resourcefor the given PSFCH format. In such a scenario, either of the followingtwo alternatives could be used, among various possibilities.

As a first possibility, the PSFCH format 0 sequence is only placed inone PRB (e.g., the first PRB) of the allocated PSFCH resource, whileleaving the remaining PRBs of the allocated PSFCH resource empty.

As a second possibility, the PSFCH format 0 sequence is duplicated overpart or all the PRBs of the allocated PSFCH resource. The same ordifferent PSFCH sequences may be used for different PRBs of theallocated PSFCH resource. In such a scenario, the transmitting UE, whichexpects to receive the HARQ feedback, may combine the PSFCH sequencesfrom different PRBs of the allocated PSFCH resource to achieve betterPSFCH decoding performance.

The selection between these first and second possibilities may beperformed using the resource pool configuration, or pre-configuration,or may be indicated in the SCI of the PSSCH transmission, among variouspossibilities.

In some instances, each PSSCH may use 1 subchannel. It is also possiblethat a PSSCH uses more than 1 subchannel. Thus, if the preceding PSSCHto PSFCH frequency domain association (per subchannel) is used, theremay be more than 1 PSFCH resource allocated for this PSSCH. In such ascenario, either of the following two alternatives could be used, amongvarious possibilities.

As a first possibility, a receiving UE only uses one of these PSFCHresource to send HARQ feedback (e.g., the first PSFCH in the frequencydomain).

As a second possibility, a receiving UE uses more than one of thesePSFCH resources to send HARQ feedback. The PSFCH format 0 sequence isduplicated over multiple PSFCH resources. The same or different PSFCHsequences may be used for different PSFCH resources. Then thetransmitting UE, which expects to receive the HARQ feedback, may combinethe PSFCH sequences from different PSFCH resources to achieve betterPSFCH decoding performance.

The selection between these first and second possibilities may beperformed using the resource pool configuration, or pre-configuration,or may be indicated in the SCI of the PSSCH transmission, among variouspossibilities.

Consider a scenario in which the sequence-based HARQ feedback, as in NRPUCCH format 0, is used for the PSFCH (i.e., short PSFCH format). Then atotal of 12 sequences with different cyclic shifts may be used in aPSFCH resource, which may span 1 PRB in frequency. Each receiver UE mayuse 4 sequences for its 2-bit HARQ ACK/NACK information. This may implythat a PSFCH resource can be multiplexed by 3 receiver UEs. For sidelinkgroup communication with a large group size (e.g., larger than 3), itmay be the case that more than one PSFCH resource will be used. ThesePSFCH resources can be frequency division multiplexed within asubchannel. It may be the case that a small configured subchannel sizemay restrict the total number of PSFCH resources within a subchannel,and subsequently restrict the total number of receiver UEs which canfeedback HARQ ACK/NACK in sidelink groupcast.

For example, if the subchannel size is 2 RBs, then it may be the casethat the sidelink groupcast HARQ ACK/NACK feedback scheme can be appliedonly if the group size is less than or equal to 6 (or 7 to include thetransmit UE in the group). If the sub-channel size is 3 RBs, then it maybe the case that the sidelink groupcast HARQ ACK/NACK feedback schemecan be applied only if the group size is less than or equal to 9 (or 10including the transmit UE in the group).

An alternative approach to enhance the HARQ ACK/NACK feedback capabilityin sidelink groupcast could include to increase the number of symbolsfor PSFCH resources. For example, two symbols could be used at the endof a slot to support more HARQ ACK/NACK feedback in sidelink groupcast.Different receiver UEs in a sidelink group may use different symbolstogether with different frequency locations of a subchannel to sendtheir HARQ feedback. Which time and/or frequency location a receiver UEcould use for this HARQ feedback may depend on the UE's in-group memberID, or its RNTI. The number of symbols used for groupcast may beconfigured during the groupcast session establishment procedure or maybe dynamically indicated in SCI for each sidelink groupcast.

As previously described herein, in ‘Option 3’ of PSCCH and PSSCHmultiplexing, the PSCCH and PSSCH share the same block of resources. Itis possible that the PSCCH occupies a few symbols at the beginning of aslot, and occupies a few resource blocks at the beginning of asubchannel.

The SCI stage 2 could be carried in the PSSCH portion of the block ofresources. In general, the SCI stage 2 could be at the beginning of aslot to achieve early decoding. Additionally, it may be the case thatthe SCI stage 2 is limited from the frequency boundary of a slot by atleast a certain amount. This may help reduce or avoid the in-bandemissions from another subchannel, and hence increase the reliability ofthe SCI stage 2 transmissions. The frequency domain offset from thesubchannel boundary can be (pre)configured or pre-defined. A transmitterUE may fill in the SCI stage 2 in the resources beyond that frequencylimited region.

If the SCI stage 1 starts from one edge of a sub-channel, then it may bethe case that the frequency limited region may be on the side of theopposite edge of the sub-channel; if the SCI stage 1 does not start fromeither edge of a sub-channel, the frequency limited region may be onboth edges of the sub-channel. The size of the frequency limited regioncan depend on the size of the sub-channel, at least according to someembodiments. FIG. 14 shows an exemplary possible SCI stage 2 resourcemapping. In the illustrated scenario, the resources at the last two REsof the sub-channel in the frequency domain are excluded from use for theSCI stage 2, e.g., to avoid in-band emission.

In the following further exemplary embodiments are provided.

One set of embodiments may include an apparatus, comprising: a processorconfigured to cause a first wireless device to: receivevehicle-to-everything (V2X) resource pool configuration information;receive V2X sidelink control information; determine a number of resourceelements allocated for a V2X physical sidelink shared channel (PSSCH)based at least in part on the V2X resource pool configurationinformation and the V2X sidelink control information; and determine atransport block size (TBS) for the V2X PSSCH based at least in part onthe number of resource elements allocated for the V2X PSSCH.

According to some embodiments, the processor is further configured tocause the first wireless device to: determine a number of resourceelements in a set of sub-channels that carry the PSSCH based at least inpart on a number of sub-channels in the set of sub-channels and a numberof resource elements in each sub-channel; determine a number ofnon-PSSCH resource elements in the set of sub-channels that carry thePSSCH; and subtract the number of non-PSSCH resource elements in the setof sub-channels that carry the PSSCH from the number of resourceelements in a set of sub-channels that carry the PSSCH to determine thenumber of resource elements allocated for the V2X PSSCH.

According to some embodiments, the non-PSSCH resource elements compriseone or more of: resource elements allocated to first stage sidelinkcontrol information; resource elements allocated to demodulationreference signals; resource elements allocated to channel stateinformation reference signals; phase tracking reference signals;resource elements allocated to a physical sidelink feedback channel;resource elements allocated to AGC and/or GAP; or resource elementsallocated to second stage sidelink control information.

According to some embodiments, the processor is further configured tocause the first wireless device to: determine whether the V2X PSSCH isbeing used for an initial transmission or a retransmission based atleast in part on the V2X sidelink control information; and determine alow density parity check (LDPC) base graph for the V2X PSSCH based atleast in part on whether the V2X PSSCH is being used for an initialtransmission or a retransmission.

According to some embodiments, the processor is further configured tocause the first wireless device to: select a same LDPC base graph forthe V2X PSSCH as used in a corresponding initial transmission if the V2XPSSCH is being used for a retransmission; and select a LDPC base graphfor the V2X PSSCH based at least in part on the TBS for the V2X PSSCH ifthe V2X PSSCH is being used for an initial transmission.

According to some embodiments, the processor is further configured tocause the first wireless device to: determine a model TBS for the V2XPSSCH, wherein the model TBS is calculated in a manner configured tonullify TBS calculation differences between PSSCH initial transmissionsand PSSCH retransmissions; and select a low density parity check (LDPC)base graph for the V2X PSSCH based at least in part on the model TBS forthe V2X PSSCH.

According to some embodiments, the processor is further configured tocause the first wireless device to: determine resource elementsallocated to second stage sidelink control information in a sub-channelthat carries the V2X PSSCH, wherein the resource elements allocated tothe second stage sidelink control information are limited from asubchannel boundary of the sub-channel by a frequency domain offset.

Another set of embodiments may include a first wireless device,comprising: at least one antenna for performing wireless communications;a radio coupled to the at least one antenna; and a processor coupled tothe radio; wherein the first wireless device is configured to: calculatea number of resource elements allocated for a vehicle-to-everything(V2X) physical sidelink shared channel (PSSCH); determine a transportblock size (TBS) for the V2X PSSCH based at least in part on the numberof resource elements allocated for the V2X PSSCH; and determine a lowdensity parity check (LDPC) base graph for the PSSCH based at least inpart on the determined TBS.

According to some embodiments, the first wireless device is furtherconfigured to: determine a channel occupancy ratio for a V2X sidelinkcommunication session; determine whether to perform a V2X sidelinktransmission for the V2X sidelink communication session based at leastin part on whether the V2X sidelink transmission would cause the channeloccupancy ratio for the V2X sidelink communication session to exceed achannel occupancy ratio limit for the V2X sidelink communicationsession.

According to some embodiments, the channel occupancy ratio for the V2Xsidelink communication session is further determined on a per prioritylevel basis.

According to some embodiments, the first wireless device is furtherconfigured to: receive configuration information indicating that slotaggregation is configured for the V2X PSSCH, wherein the configurationinformation further indicates a demodulation reference signal (DMRS)configuration for each of a first slot of the V2X PSSCH, one or moremiddle slots of the V2X PSSCH, and a last slot of the V2X PSSCH.

According to some embodiments, the first wireless device is furtherconfigured to: receive configuration information indicating that slotaggregation is configured for the V2X PSSCH, wherein the configurationinformation further indicates a starting demodulation reference signal(DMRS) symbol and a gap between DMRS symbols for the V2X PSSCH.

Yet another set of embodiments may include a method, comprising: by afirst wireless device: determining a number of resource elementsallocated for a vehicle-to-everything (V2X) physical sidelink sharedchannel (PSSCH); determining a transport block size (TBS) for the V2XPSSCH based at least in part on the number of resource elementsallocated for the V2X PSSCH; and determining a low density parity check(LDPC) base graph for the PSSCH based at least in part on the determinedTBS.

According to some embodiments, the method further comprises: determiningif one or more resources are reserved for V2X sidelink transmission by asecond wireless device, wherein the second wireless device is adestination wireless device for a V2X sidelink transmission by the firstwireless device; determining if one or more resources are reserved forV2X sidelink transmission to the first wireless device and performingresource selection for the V2X sidelink transmission by the firstwireless device, wherein if one or more resources are reserved for V2Xsidelink transmission by the second wireless device, any resources in asame time slot as the one or more resources reserved for V2X sidelinktransmission by the second wireless device are excluded from theresource selection for the V2X sidelink transmission by the firstwireless device, wherein if one or more resources are reserved for V2Xsidelink transmission to the first wireless device, any resources in asame time slot as the one or more resources reserved for V2X sidelinktransmission to the first wireless device are excluded from the resourceselection for the V2X sidelink transmission by the first wirelessdevice.

According to some embodiments, the method further comprises: determiningrelative priority levels of the V2X sidelink transmission by the secondwireless device, the V2X sidelink transmission to the first wirelessdevice, and the V2X sidelink transmission by the first wireless device;and determining whether to exclude any resources in a same time slot asthe one or more resources reserved for V2X sidelink transmission by thesecond wireless device or any resources in a same time slot as the oneor more resources reserved for V2X sidelink transmission to the firstwireless device from resource selection for the V2X sidelinktransmission by the first wireless device based at least in part on therelative priority levels of the V2X sidelink transmission by the secondwireless device, the V2X sidelink transmission to the first wirelessdevice, and the V2X sidelink transmission by the first wireless device.

According to some embodiments, the method further comprises: performingresource selection for a V2X sidelink transmission by the first wirelessdevice; determining if one or more resources are reserved for V2Xsidelink transmission by a second wireless device, wherein the secondwireless device is a destination wireless device for the V2X sidelinktransmission by the first wireless device; determining if one or moreresources are reserved for V2X sidelink transmission to the firstwireless device; and removing any resources in a same time slot as theone or more resources reserved for V2X sidelink transmission by thesecond wireless device and any resources in a same time slot as the oneor more resources reserved for V2X sidelink transmission to the firstwireless device from the resources selected for the V2X sidelinktransmission by the first wireless device.

According to some embodiments, the method further comprises: performingresource selection for a V2X sidelink transmission by the first wirelessdevice; determining if one or more resources are reserved for V2Xsidelink transmission by a second wireless device, wherein the secondwireless device is a destination wireless device for the V2X sidelinktransmission by the first wireless device; determining if one or moreresources are reserved for V2X sidelink transmission to the firstwireless device; and dropping the V2X sidelink transmission by the firstwireless device if any resources selected for the V2X sidelinktransmission by the first wireless device are in a same time slot as theone or more resources reserved for V2X sidelink transmission by thesecond wireless device or if any resources selected for the V2X sidelinktransmission by the first wireless device are in a same time slot as theone or more resources reserved for V2X sidelink transmission to thefirst wireless device.

According to some embodiments, the method further comprises: determininga slot in which feedback for the V2X PSSCH is expected, wherein the slotin which feedback for the V2X PSSCH is expected is determined as a firstslot in which a V2X physical sidelink feedback channel (PSFCH) ispresent after a PSFCH gap, wherein a value of the PSFCH gap isdetermined based at least in part on a periodicity of the V2X PSFCH.

According to some embodiments, the method further comprises: determiningone or more V2X physical sidelink feedback channel (PSFCH) frequencyresources in which feedback for the V2X PSSCH is expected, wherein theV2X PSFCH frequency resources in which feedback for the V2X PSSCH isexpected are determined based at least in part on a periodicity of theV2X PSFCH.

According to some embodiments, the method further comprises: determiningone or more V2X physical sidelink feedback channel (PSFCH) frequencyresources in which feedback for the V2X PSSCH is expected, wherein theV2X PSFCH frequency resources in which feedback for the V2X PSSCH isexpected are determined based at least in part on a group size of agroupcast group associated with the V2X PSSCH.

A further exemplary embodiment may include a method, comprising:performing, by a wireless device, any or all parts of the precedingexamples.

Another exemplary embodiment may include a device, comprising: anantenna; a radio coupled to the antenna; and a processor operablycoupled to the radio, wherein the device is configured to implement anyor all parts of the preceding examples.

A further exemplary set of embodiments may include a non-transitorycomputer accessible memory medium comprising program instructions which,when executed at a device, cause the device to implement any or allparts of any of the preceding examples.

A still further exemplary set of embodiments may include a computerprogram comprising instructions for performing any or all parts of anyof the preceding examples.

Yet another exemplary set of embodiments may include an apparatuscomprising means for performing any or all of the elements of any of thepreceding examples.

Still another exemplary set of embodiments may include an apparatuscomprising a processor configured to cause a wireless device to performany or all of the elements of any of the preceding examples.

It is well understood that the use of personally identifiableinformation should follow privacy policies and practices that aregenerally recognized as meeting or exceeding industry or governmentalrequirements for maintaining the privacy of users. In particular,personally identifiable information data should be managed and handledso as to minimize risks of unintentional or unauthorized access or use,and the nature of authorized use should be clearly indicated to users.

Embodiments of the present disclosure may be realized in any of variousforms. For example, some embodiments may be realized as acomputer-implemented method, a computer-readable memory medium, or acomputer system. Other embodiments may be realized using one or morecustom-designed hardware devices such as ASICs. Still other embodimentsmay be realized using one or more programmable hardware elements such asFPGAs.

In some embodiments, a non-transitory computer-readable memory mediummay be configured so that it stores program instructions and/or data,where the program instructions, if executed by a computer system, causethe computer system to perform a method, e.g., any of a methodembodiments described herein, or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets.

In some embodiments, a device (e.g., a UE 104) may be configured toinclude a processor (or a set of processors) and a memory medium, wherethe memory medium stores program instructions, where the processor isconfigured to read and execute the program instructions from the memorymedium, where the program instructions are executable to implement anyof the various method embodiments described herein (or, any combinationof the method embodiments described herein, or, any subset of any of themethod embodiments described herein, or, any combination of suchsubsets). The device may be realized in any of various forms.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

What is claimed is:
 1. A method, comprising: a wireless device,determining a number of resource elements (REs) allocated for a NewRadio (NR) physical sidelink shared channel (PSSCH); and determining atransport block size (TBS) for the NR PSSCH based at least in part onthe number of REs for PSSCH allocated for the NR PSSCH, wherein thenumber of REs allocated for the NR PSSCH is based on a total number ofREs in channel resources for the NR PSSCH minus non-PSSCH REs.
 2. Themethod of claim 1, wherein the non-PSSCH REs comprise REs allocated to afirst stage sidelink control information, resource elements allocated todemodulation reference signals, and resource elements allocated to asecond stage sidelink control information.
 3. The method of claim 1,further comprising: the wireless device, determining a number of REs ina set of sub-channels that carry the NR PSSCH based at least in part ona number of sub-channels in the set of sub-channels and a number of REsin each sub-channel; determining a number of non-PSSCH REs in the set ofsub-channels that carry the NR PSSCH; and subtracting the number ofnon-PSSCH REs in the set of sub-channels that carry the NR PSSCH fromthe number of REs in a set of sub-channels that carry the NR PSSCH todetermine the number of resource elements allocated for the NR PSSCH. 4.The method of claim 1, further comprising: the wireless device,determining whether the NR PSSCH is being used for an initialtransmission or a retransmission based at least in part on NR sidelinkcontrol information.
 5. The method of claim 4, further comprising: thewireless device, determining a low density parity check (LDPC) basegraph for the NR PSSCH based at least in part on whether the NR PSSCH isbeing used for an initial transmission or a retransmission.
 6. Themethod of claim 5, further comprising: the wireless device, selecting asame LDPC base graph for the NR PSSCH as used in a corresponding initialtransmission when the NR PSSCH is being used for a retransmission; andselecting a LDPC base graph for the NR PSSCH based at least in part onthe TBS for the NR PSSCH when the NR PSSCH is being used for an initialtransmission.
 7. The method of claim 1, further comprising: the wirelessdevice, determining a model TBS for the NR PSSCH, wherein the model TBSis calculated in a manner configured to nullify TBS calculationdifferences between NR PSSCH initial transmissions and NR PSSCHretransmissions; and selecting a low density parity check (LDPC) basegraph for the NR PSSCH based at least in part on the model TBS for theNR PSSCH.
 8. The method of claim 1, further comprising: the wirelessdevice, determining REs allocated to second stage sidelink controlinformation in a sub-channel that carries the NR PSSCH, wherein the REsallocated to the second stage sidelink control information are limitedfrom a subchannel boundary of the sub-channel by a frequency domainoffset.
 9. A wireless device, comprising: at least one antenna forperforming wireless communications; a radio coupled to the at least oneantenna; and a processor coupled to the radio; and wherein the wirelessdevice is configured to: determine a number of resource elements (REs)allocated for a New Radio (NR) physical sidelink shared channel (PSSCH);and determine a transport block size (TBS) for the NR PSSCH based atleast in part on the number of REs for PSSCH allocated for the NR PSSCH.10. The wireless device of claim 9, wherein the number of REs allocatedfor the NR PSSCH is based on a total number of REs in channel resourcesfor the NR PSSCH minus non-PSSCH REs.
 11. The wireless device of claim10, wherein the non-PSSCH REs comprise REs allocated to a first stagesidelink control information, resource elements allocated todemodulation reference signals, and resource elements allocated to asecond stage sidelink control information.
 12. The wireless device ofclaim 9, wherein the wireless device is further configured to: determinea channel occupancy ratio for an NR sidelink communication session; anddetermine whether to perform an NR sidelink transmission for the NRsidelink communication session based at least in part on whether the NRsidelink transmission would cause the channel occupancy ratio for the NRsidelink communication session to exceed a channel occupancy ratio limitfor the NR sidelink communication session.
 13. The wireless device ofclaim 12, wherein the channel occupancy ratio for the NR sidelinkcommunication session is further determined on a per priority levelbasis.
 14. The wireless device of claim 9, wherein the wireless deviceis further configured to: receive configuration information indicatingthat slot aggregation is configured for the NR PSSCH, wherein theconfiguration information further indicates a demodulation referencesignal (DMRS) configuration for each of a first slot of the NR PSSCH,one or more middle slots of the NR PSSCH, and a last slot of the NRPSSCH.
 15. The wireless device of claim 9, wherein the wireless deviceis further configured to: receive configuration information indicatingthat slot aggregation is configured for the NR PSSCH, wherein theconfiguration information further indicates a starting demodulationreference signal (DMRS) symbol and a gap between DMRS symbols for the NRPSSCH.
 16. An apparatus, comprising: a memory; and a processor incommunication with the memory and configured to: determine a number ofresource elements (REs) allocated for a New Radio (NR) physical sidelinkshared channel (PSSCH); and determine a transport block size (TBS) forthe NR PSSCH based at least in part on the number of REs for PSSCHallocated for the NR PSSCH, wherein the number of REs for PSSCH isbased, at least in part, on a number of non-PSSCH REs, wherein thenon-PSSCH REs comprise REs allocated to a first stage sidelink controlinformation, resource elements allocated to demodulation referencesignals, and resource elements allocated to a second stage sidelinkcontrol information.
 17. The apparatus of claim 16, wherein the numberof REs allocated for the NR PSSCH is based on a total number of REs inchannel resources for the NR PSSCH minus the non-PSSCH REs.
 18. Theapparatus of claim 16, wherein the processor is further configured to:determine a number of REs in a set of sub-channels that carry the NRPSSCH based at least in part on a number of sub-channels in the set ofsub-channels and a number of REs in each sub-channel; determine a numberof non-PSSCH REs in the set of sub-channels that carry the NR PSSCH; andsubtract the number of non-PSSCH REs in the set of sub-channels thatcarry the NR PSSCH from the number of REs in a set of sub-channels thatcarry the NR PSSCH to determine the number of resource elementsallocated for the NR PSSCH.
 19. The apparatus of claim 16, wherein theprocessor is further configured to: determine a model TBS for the NRPSSCH, wherein the model TBS is calculated in a manner configured tonullify TBS calculation differences between NR PSSCH initialtransmissions and NR PSSCH retransmissions; and select a low densityparity check (LDPC) base graph for the NR PSSCH based at least in parton the model TBS for the NR PSSCH.
 20. The apparatus of claim 16,wherein the processor is further configured to: determine REs allocatedto second stage sidelink control information in a sub-channel thatcarries the NR PSSCH, wherein the REs allocated to the second stagesidelink control information are limited from a subchannel boundary ofthe sub-channel by a frequency domain offset.